TRITONIADA. 381 
SuporDER ATOLOBRANCHIAT A. 
Branchiz variable, generally upon the sides of the back; not 
as in the last family, in a circle surrounding the anal orifice. 
Famity TRITONIAD 4. 
Animal with laminated, plumose, or papillose gills, arranged 
along the sides of the back; tentacles retractile into sheaths ; 
lingual membrane with one central and numerous lateral teeth ; 
orifices on the right side. 
TRITONIA, Cuvier. 
Syn.—Candiella, Gray. 
Distr.—20 sp. Northern seas, Polynesia, Red Sea. Under 
stones at low-water to 25 fathoms. 7. Hombergii, Cuvier, found 
onthe English scallop-banks, attains a length exceeding 6 inches, 
T. plebeia, Johnst. (xc, 14). 
Animal elongated; tentacles with branched filaments; veil 
fimbriately digitated; gills in single series on a ridge down 
each side of the back; mouth armed with horny jaws; stomach 
simple, liver compact. 
MARIONIA, Vayssiere, 1879. Body elongate, sides compressed, 
mantle none; velum small, ramose,in a dorsal line; maxille cor- 
neous; stomach armed with cultriform teeth. 7. Berghi, Vayss. 
Gulf of Marseilles. 
CALIPHYLLA, Costa. Body long, narrow; tentacles two, folia- 
ceous, longitudinally convolute; labial border bilobed; branchiz 
foliaceous, vascular, numerous, in irregular, longitudinal series ; 
anus on the right side behind the genital orifice. Distr.—C. 
Mediterranea, Costa. Mediterranean. 
NEMOCEPHALA, Costa. Body Tritoniiform; anterior margin of 
the head semicircular, six-digitate, or divided into six simple, 
cylindrical tentaculiform processes ; tentacles ramose, retractile 
into sheaths; branchiz arborescent, on both sides of the back in 
single longitudinal series. Differs from Dendronotus in the six 
filaments being simple, not branched. Distv.—T. marmorata, 
Costa. Mediterranean. 
HANCOCKIA, Gosse. Body linear, scarcely palliate, head pro- 
duced on each side into a broad, flat, many-fingered veil; dorsal 
tentacles with laminated bulbs, retractile within sheaths; 
branchie three pairs, foliate, pinnatifid, infolding, remotely 
situated. on the subpalliate margin of the back; foot linear, 
grasping. Distr.—T. eudactylota, Gosse. 

Tevuys, Linn. 
Etym.— Tethys, the sea (personified }. 
_ Syn.—Fimbria, Bohadsch. . 
Distr.—T. fimbriata, L. (xc, 15). Mediterranean. — Attains a 
